What is paulownia wood?
The Wood Guide · The wood register
Broadleaf wood · referencePaulownia wood
Kiri in Japan, the princess tree in English. A broadleaf wood that is lighter than most softwoods, hardly moves and is remarkably slow to catch fire.
- Paulownia tomentosa
- 270–300 kg/m³
- Only ignites at around 400 °C
Anna Paulowna treePaulownia tomentosa
Paulownia wood
Kiri in Japan, the princess tree in English. A broadleaf wood that is lighter than most softwoods, hardly moves and is remarkably slow to catch fire.
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Paulownia in brief
Also called royal paulownia, princess tree or kiri. A wood with an unusual combination of properties — and a long Japanese history.
At 270 to 300 kg/m³, paulownia is much lighter than spruce, and yet it is a broadleaf wood. Its strength-to-weight ratio is exceptional: it carries far more than you would expect at this weight.
What makes it truly special is its stability. Paulownia hardly shrinks or swells with changing humidity. A paulownia door or drawer does not stick in summer or rattle in winter.
In Japan a paulownia was traditionally planted when a daughter was born, and felled when she married to make a tansu chest from it. Not only out of sentiment: the wood is slow to catch fire and the chest swells shut with moisture, so the contents could survive a house fire.
- Botanical
- Paulownia tomentosa and relatives
- Other names
- Kiri, princess tree, empress tree
- Density
- 270–300 kg/m³ — very light
- Growth
- up to several metres a year; harvestable in 7–10 years
- Ignition
- around 400 °C, against about 250 °C for most species
- Durability
- class 4 — not for exposed outdoor use
To be fair: paulownia is soft. A tabletop gets dents the very first time it is used, and for anything that is touched or loaded it is not a good choice. It excels where weight and stability count, not where hardness counts.
Four unusual properties
Very light
270 to 300 kg/m³ — lighter than spruce (450) and even lighter than many softwoods, while botanically it is a broadleaf wood.
Exceptionally stable
Very low shrinkage with changing humidity. That is why it is used in drawers, doors and instrument cases.
Fire-resistant, for a wood
It only ignites at around 400 °C, whereas most wood species catch fire at around 250 °C. The explanation is the open cell structure with a high proportion of air.
Fast-growing
Metres a year in the first growing seasons, harvestable after seven to ten years. That makes plantations quickly renewable.
That same vigour makes paulownia an invasive species in parts of Europe and North America: it spreads easily by seed and crowds out native vegetation. Planting therefore belongs in managed plantations, not in the wild.
Where paulownia is used
| Use | Why paulownia | Distinctive |
|---|---|---|
| Surfboards | Light and resilient | Sustainable alternative to foam cores |
| Musical instruments | Light with good sound transmission | The Japanese koto is traditionally made of kiri |
| Drawers and cabinet interiors | Hardly moves | Does not stick with changes in moisture |
| Japanese tansu chests | Stable and fire-resistant | Centuries-old tradition |
| Model making and aviation | Strength-to-weight ratio | Where balsa is too soft |
| Sauna parts | Does not get hot to the touch | Low thermal conductivity |
With durability class 4 and a soft surface, paulownia belongs indoors. For outdoors, look at pressure-treated spruce, acacia or teak.
Frequently asked questions about paulownia wood
Is paulownia hardwood or softwood?
Botanically it is a broadleaf wood, and therefore a hardwood — while being softer and lighter than most softwoods. Another example of why the division into hardwood and softwood says nothing about hardness.
Can paulownia be used outdoors?
To a limited extent. It is in durability class 4, so unsheltered it lasts only a few years. Sheltered and treated it can work, for example on a covered veranda.
Is it true that paulownia is fire-resistant?
Relatively. It only ignites at around 400 °C, while most wood species catch fire at around 250 °C. That makes it more fire-resistant than other wood, not fireproof.
Why is it called the princess tree?
The botanical name honours Anna Pavlovna (Anna Paulowna), daughter of Tsar Paul I and Queen of the Netherlands. In Japan the same tree is called kiri and appears on the government seal.
Paulownia in perspective
A reference species with a story — light, stable, and not for the garden.
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Paulownia tomentosa — Agnieszka Kwiecień, Nova, CC BY-SA 4.0 · Photo via Wikimedia Commons: Paulownia tomentosa — Jean-Pol GRANDMONT, CC BY 3.0